Maybe. It all depends on how strict you wish to be with yourself when it comes to verbatim quotes. The really strict line is make any change to a quote and you are no longer quoting your source. The more liberal stance would be minor changes, such as you are suggesting, that do not change to meaning of the quote are permissible. Of course you may want to attribute it in a manner similar to what joyR suggested.
Despite Dominions Son's dislike of non-fictional epigraphs, my readers seem to appreciate them, most often through comments about the more humorous ones. But then, I pick epigraphs which either highlight what happens within the chapter, putting a particular slant on it, or in this case, takes a humorous twist on the chapter's plot. I'm sure that many readers don't bother with them at all, but when feedback suggests something works, you tend to continue (i.e. silence=death, feedback=repetition).
But whenever there's a question about the epigraph (most often when the quote is questioned, or has been misattributed) I include an asterisk after the quote, so readers can check my included Bibliography to determine what's wrong with the standard quote. But mostly, the bibliography is there only if a reader is interested in using the quote themselves. However, I thoroughly document each quote I use (whenever possible, as I sometimes include those I can't authenticate and document).
The issue with using something like "to misquote XXX" is that the epigraph is not included as part of the story, instead, it stands alone at the top of each chapter, with only the author's name. The reader can investigate the sources in the Bibliography, but I don't pretend many readers will really care that much, which is why I'll call attention to my fudging with the quote.
In the end, it'll look like this example.
In this case, it's clear what the original (translated) words were, while it's equally obvious how I mucked with it, plus a link to the original source. I'm not sure how I can be any more clear about what I'm doing.
You can also change individual words so that a quote makes sense, by putting the word you've changed in square brackets [ ].
That's an interesting, though less clear approach: In that case my quote would appear as:
Doubt is a pain too lonely to know that faith is [her] twin [sister].
That approach works, but it's unclear how I changed it, or why (i.e. to fit the contents of the chapter, as I'm highlighting how the character's respond to my main character, rather than clarifying the language itself.
Still, it is more straightforward, and is an accepted standard, so a few readers may be familiar with it's usage.
However, in the end, there is NO evident that Khalil ever wrote these words, despite it's widespread attribution to him, so I'm likely to drop it entirely. Still, it's nice knowing how to approach this issues in the future.